Cyclopropane carboxylic acid derivatives are generally represented by the following formula II: ##STR3## wherein R.sub.1, R.sub.2, R.sub.2', R.sub.3 and R.sub.3', which may be the same or different, each is a hydrogen atom, a linear or branched C.sub.1 -C.sub.10 alkyl chain, phenyl, acetyl or halogen.
The compounds represented by the formula II have been widely used as a functional group having a specific activity in the compounds recently used in various kinds of medicines and agricultural medicines. Various kinds of derivatives, such as cyclopropane carboxylic acids and ester derivatives thereof, cyclopropane methanol have been widely used in commercialized pyrenoids insecticides and antibiotics, and are very important in medicine/agricultural medicine fields in various forms.
In addition, vitamin E (DL-alpha-tocopherol), represented by the following formula III, is a physiologically essential vitamin among the various vitamins, like vitamin A, C, D, K, beta-carotene and so forth. Vitamin E is relatively complicated in its structure and is widely used as a nutrient, medicines, parturifacient, antioxidant and so forth: ##STR4##
In spite of its importance, Vitamin E, a compound possessing a benzene ring to which hydroxy group binds, is unstable because it itself is easily oxidized. Tocopherol quinone, an oxidized product of vitamin E, no longer has the biological activity of vitamin E. Thus, because storage and management of vitamin E in itself are difficult, there are many attempts in order to increase stability of vitamin E by converting it to other derivative forms.
Representatives of the above mentioned derivatives are esters, which have an enhanced stability by converting the hydroxyl group in phenol ring, specially weak to oxidize, to an ester form. In the above manner, various tocopherols have been made, and examples of such derivatives include tocopherol acetate, tocopherol succinate, tocopherol phosphate Na.sup.+ salt and so on, which are represented by the following formula IV: ##STR5##
Because these esters have pharmaceutically acceptable stability in addition to being very easy to handle, they are effectively used as replacements for vitamin E.
Upon oral administration, the vitamin E esters are absorbed into the intestinal track and hydrolyzed completely, that is, into free tocopherol and acids by pancreatic enzymes and intestinal enzymes. Thus, the vitamin E esters are absorbed in the form of free tocopherol into the living body. In other words, the esters, when used as replacements for vitamin E in the living body, are converted into free vitamin E and absorbed in the living body, so that the biological effect they have on the living body is practically equivalent to that of vitamin E.
Vitamin E derivatives represented by the following formula V has been filed by the present applicant on Apr. 28, 1997 in Korea under Patent Application No. 97-15961: ##STR6## wherein R.sub.4 and R.sub.5 which may be the same of different, each is a hydrogen atom or a linear or branched C.sub.1 -C.sub.4 alkyl chain.